Brake mechanism



C. F. BAISCH BRAKE HECHANISM July 4, 1939.

2 Sheets-Sheet 1 Filed July 6, 1937 J mh, m me m Ew o. wa n 100 A Ul. HM

a C w :Y Y

July 4, 1939.6 Q BNSCH 2,164,866

BRAKE IECHANISM Filed July 6, 1957 2 Sheets-Sheet 2 fig. 4l.

' l INVENTOR. BY Carl Fazfsch M @M ATTORNEY. 5

Patented July 4, 1939 UNITED STATES PATENT GFFICE BRAKE MECHANISM Carl F. Baisch, Detroit, Mich.,

soy-Hayes Wheel Company,

assignor to Kel- Detroit, Mich., a

corporation of Delaware Application July 6, 1937, Serial No. 152,249

9 Claims.

It is one of the principal objects of the present' invention to provide a compact, simple adjustment anchor device composed of a relatively few parts capable of being readily assembled and installed on the backing plate of the brake drum between adjacent ends of the friction means.

Another object of this invention which contributes materially to simplifying the construction of the adjustment anchor device consists in the provision of a cam rotatably supported on the backing plate between the ends of the fric- Ation means and having circumferentially spaced cam surfaces respectively engaging said ends of the friction means to effect outward movement of vthe latter ends upon rotation of the cam in one direction.

A further advantageous feature of the present invention resides in the provision of brake mech'- anism of the general character previously set forth wherein the adjacent ends of the friction means directly engage the cam surfaces on the cam in such a manner as to permit independent movement of the ends of the friction means radially of the drum. With this construction, the links hereinbefore provided between the adjustable member and the adjacent ends of the friction means are eliminated and, as a result, the number of parts are not only reduced, but the internal friction is minimized.

Still another object of this invention resides in the provision of an adjustment anchor device supported upon the backing plate of the brake drum for shifting movement circumferentially of the drum and thereby permitting the brake 'torque to be transferred from one shoe to the other through the adjustment device when the latter is employed in association with a servo brake.

A further object of this invention consists in the provision of brake mechanism having brake yfriction means of the shoe type wherein one of the shoes wears to a greater extent than the other shoe and wherein provision is made in the adjustment anchor device for adjusting the shoe having the greatest wear at a faster rate than the other shoe. In accordance with the present invention, the cam surface on the adjustable cam engaging the shoe having the greatest wear has a rise greater than the rise of the cam surface engaging the other shoe by an amount predetermined to compensate for the differential wear of (Cl. 18S-79.5)

the shoes and thereby effect uniform clearance between the shoes and the braking surface of the drum.

In addition to the foregoing, th'e present invention contemplates an improved means for preventing accidental rotation of the cam and for indicating predetermined increments of adjustment. The means for accomplishing this result, as well as the foregoing and other objects, will be made more apparent as this description proceeds, especially when considered in connection with the accompanying drawings, wherein:

Figure 1 is a side elevational view of brake mechanism equipped with-an adjustment anchor device constructed in accordance with this invention;

Figure 2 is a sectional view taken substantially on the plane indicated by the line 2 2 of Figure 1;

Figure 3 is a sectional View taken substantially on the plane indicated by the line 3 3 of Figure Figure 4 is a sectional view taken substantially on the plane indicated by the line 4-4 of Figure 1; and

Figure 5 is a fragmentary side elevational view of the adjustment anchor device having certain parts broken away for the sake of clearness.

In Figure 1 of the drawings, I have shown a revoluble brake drum Il] having an axially extending annular brake flange II and having a backing plate I2 closing the rear side of the drum. In accordance with conventional practice, the backing plate I2 is secured against rotation and supports the brake mechanism within the drum.

The brake mechanism includes brake friction means I3 and the latter, in turn, comprises a pair of brake shoes supported upon the backingplate with the opposite ends spaced from each other circumferentially of the drum. Upon reference to Figure 2, it will be noted that the brake shoes are substantially T-shaped in cross section having axially extending head portions I4 extending adjacent the inner surface of the brake flange I I and having radially inwardly extending web portions I5. As is usually the case, a brake lining I6 of the desired coefficient of friction is secured to the outer surface of the head portion I4 of each shoe for frictional engagement with the brake flange Il when the shoes are moved outwardly relative to the drum.

The brake mechanism also includes an actuator I1 for expanding the shoes outwardly against the brake flange and this actuator will be more fully hereinafter set forth. At this time it may it will be noted that the adjustment device is prof vided with a stem 2| having a portion 22 located exteriorly of the backing plate, where it may-be tween the ends of the friction means through an opening 24 in the backing plate., Keyed to the rotatable stem 2| by means of a key 2| is a cam 25 and 26 respectively engageablewith the adjacent ends of the primary and secondary shoes 2T and 28. Each cam surface has a constantrise and is effective upon rotation of the stem in the,- direction of the arrowV 29 to move the shoe in en-l gagement therewith toward the brake flange AV|| about an abutment 3U secured to the backingr` plate I2 between the actuator ends of thecshoes. Upon referenceto Figure l, it ywill be noted that the actuator ends ofthe shoes are formed with arcuate recesses 32 of a radiusv predetermined to pivotally engage the'opposite sidesjof the abutment and are maintained into engagement with the abutment by means of the retracting spring 33 interconnectingtheactuator en ds of the shoes. The adjustment ends of the brake shoes are yieldably maintained into engagement with the,

cam surfaces by means of the retraction springs 34 and 35 having the outer ends respectively connected to the primary and secondary shoes and having the innerends anchored on the backing plate.

Upon reference to Figure 5, it will be noted that the adjustment ends of the shoes,

are substantially straight as indicated by the reference character 31 andhave a direct bearing engagement with the cam surfaces Whiclr permits independent radial shifting movementy of the shoes relative to the cam. This construction is advantageous-vin that it eliminatesmthe;

links hereinbefore provided for accomplishing the above result and thereby not only reduces the number of parts involved,- but also minimizes internal friction.

The inner end of the stem 2| extends through an opening in a plate 39 secured on the stem by means of a nut 40 and having a flange 4| extending axially outwardly from the radially outer edge thereof. in the direction of the circumference of the drum and overlaps the radially outer Wall 42 of a deL c pression 43 formed in the backing plate 2 of the drum in the region of the adjustment vdevice to house the axially outer end ofthe stemL l'I'he plate 39 is triangular in shape in elevation and is prevented from rotation with the stem y 2,2 by engagement of the flange 41| with the radially outer wall of the depressedgportionl` in the K backing plate.

In the present instance, a flexible spring disc 44 is secured against the axially inner side of the` plate 39 by means of the nut 49, and this discjs keyed to the stem 2 2 for rotation therewith as a,y

unit by means of a key 22 in the form of a projection on the disc extendinginto the same recess 40 in the stem 22 occupied bythe key42l'. yUpon, reference to Figure 3, it will be noted that the ners-of the triangular plate 39.

- engagement with the brake flange.

Afer from one shoe to the .,other.

The flange 4| iselongated A to compensate for this difference in-wear.

disc is provided with a flexible peripheral portion 45 held into engagement with the axially inner side of the plate 39 under tension by fashioning the disc to form an annular bowed portion 46 surrounding the nut 49. Referring again to Figure 1 of the drawings, it will be noted that the flexible peripheral portion 45 of the disc is fashioned to formaseries of circumferentially spaced detents 4l adapted to successively engage in one of the three grooves 48 formed at the cor- Inasmuch as the disc 44 rotates as a unit with the stem and in l view ofthe'lfact that the plate 39 is held from conveniently manipulated to rotate the stemandf having a portion 23 extending into the'd-rum'lbe-f;

rotation-,it follows,v that the detents cooperate with-,thegroovesin not only yieldably resisting yaccidental-rotation .off the stem, but to also indi- `cate ,predetermined increments of adjustment of the cam 24.

24 having diametrically opposed cam surfaces;

Attentionmay also be called to the fact at this .Y time that the plate 39 cooperates with the adja- ,centside'of the backing plate to retain the adjustment ends of the shoes intofengagement with their respective cam surfaces.- `In otherA words,.-

axial displacement of the adjustment-\ends-of the shoes relative to the drum isv prevented by the primary shoe to the secondary shoe through Vthe plate 39, land similar; displacement of the the @am 24'. In detail, the opening'za in the backingplate |2 is elongated in the direction n of forward rotation of the drum in order to permit shifting movementfof the stem,with the brake shoes when the latter yareexpanded into In this connection, it is to be noted that the'flange on the plate 39 merely slides against the wall 42 ofl the c depressed portion'on the backing plate when the adjustmentv device is shifted by the braking torque. Also, when vthis constructionv is pro;-

force on the adjustment end of the secondary shoe than the'retract-ion spring 34 so that in the vided, the springr 35 isdesigned` to exert a greater i released position of the brake, the stem is main- A tained into abutting engagement with the wall 5| of the slot. As a consequence, when the,

brake isapplied during rotationof the drum in .the ',reverse, direction, the adjustment device forms an anchor and there is no torquetrans- In other words, a symmetrical brake results when the shoes are actuated during reverse rotationof the drum.

In brakes ofthe above type, the friction lining of the primary slioelfl wearsto aA greaten extent thanjthe frictionlining of the secondary shoe, 28 and, in some `Cases, it` is` desirablewto come.. pensate for this differential wear during.adjust- In the present instance, the4 frise of the-.camfsurface25 is greater ythan the rise-of the'cam surface-26 so. thatfthe primary shoe ismovedfoutwardlyby thecam124 at afment of the shoes.

faster -rate thanz'the-secondaryshoe :28.'1In

Wear between the linings-of thetwo shoesfmay rate sufficiently greater than the secondary shoe procedure vresults in more uniform adjustment of the brake and appreciably-increases4 braking .65' 'practicegfthe-actual difference'ain the -rate `of Such eiciency throughout the life of the brake linings.

Although the adjustment anchor device is by no means limited to use in a brake having a particular type of actuator, nevertheless, for the purpose of illustrating the present invention, I have shown the actuator l1 as being of the leverage type. Briefly described, the actuator I1 comprises a lever 55 having the radially outer end pivotally connected to the end'of the secondary shoe 28 at a point 56 adjacent the abutment 30 in close proximity to the diameter of the brake flange, and having the radially inner end connected to an operating cable 51 in the manner designated by the reference character 58. Upon reference to Figure 1, it will be noted that the lever 55 is connected to the abutment end of the primary shoe 21 by means of a spreader link 59. The spreader link 59 is pivotally connected to the lever 55 at a point 60 positioned adjacent the point of pivotal connection 56 of the lever with the secondary shoe and the opposite end of the spreader link is pivotally connected to the primary shoe at a point 6I located adjacent the abutment 30 in close proximity to the diameter of the brake ange. The link is curved longitudinally to provide clearance for the abutment 30 and at the same time permit the aforesaid locations of the pivots 60 and 6l.

Assuming that the drum is rotating in the forward direction indicated by the arrow I8 in Figure 1 and assuming that the radially inner end of the lever 55 is moved in the direction of the arrow 63 by the cable 51, it will be noted that the lever 55 fulcrums about the point 56 and moves the abutment end of the primary shoe outwardly into engagement with the b-rake flange. During this operation, the actuator end of the secondary shoe is maintained into engagement with the abutment 30 by means of a spring 64 having one end connected to the secondary shoe adjacent the actuator end thereof and having the other end connected to the lever 55 adjacent the radially inner end of the latter. The spring 64 is lighter than the spring 35 so as not to interfere with the operation of the latter in maintaining the adjustment anchor device in abutting engagement with the side 5I of the opening 24 through the backing plate.

Movement of the primary shoe into engagement with the brake flange in the above manner effects a servo action and the latter tends to shift the primary shoe in the direction of rotaf tion. In the present instance, shifting movement of the primary shoe in the forward direction of rotation of the brake drum is permitted by reason of the enlarged opening 24 and torque is transferred from the primary shoe through the cam 24 to the secondary shoe, with the result that the latter also wraps into engagement with the brake ange. Assuming now that the brake drum is rotating in the reverse direction and that the lever is operated by the cable to expand the shoes into engagement with the brake ange, it will be noted that after the shoes have been initially engaged with the brake flange, the lever 55 fulcrums about the point 60 on the secondary shoe and a reduction in leverage is accordingly effected. It will also be observed that the adjustment anchor device is in abutting engagement with the wall 5I of the opening 24 so that no torque is transferred from one shoe to the other. In other words, when the brake drum is rotating in the reverse direction, the brake mechanism becomes symmetrical and there is practically no servo action.

Particular reference has been made above to the location of the pivots 56, 60, and Bl relative to the abutment 30 and diameter of the brake flange Il. By locating these pivot points as close to the drum diameter as possible, sufficient leverage is provided with a link having a length suitable to permit extending the cable 51 between the abutment 35 and the opening through the backing plate through which the spindle or axle extends. Also, by arranging the pivots in predetermined relation to the abutment 30, any displacement of the radially inner end 55 of the lever caused by adjusting the brake shoes is negligible and, as a consequence, it is not necessary to adjust the length of the cable 51 when the brake shoes are adjusted by the device 2li.

What I claim as my invention is:

1. In brake mechanism, a revoluble brake drum, a backing plate for the drum fixed against rotation, brake friction means supported on the backing plate Within the drum for shifting movement circumferentially of the drum and having spaced ends, an adjustment device for the friction means including a member rotatably supported on the backing plate between the ends of the friction means and mounted for shifting movement with the friction means, said member having diametrically opposed cam surfaces respectively engageable with the ends of the friction means and effective upon rotation of the member in one direction to move the ends o-f the friction means outwardly relative to the drum, means accessible from a point exteriorly of the drum for rotating said member, and means for indicating predetermined increments of adjustment of the friction means by said member.

2. In brake mechanism, a revoluble brake drum, brake shoes supported within the drum for shifting movement circumferentially of the drum` and having different rates of wear, an, adjustment device for the brake shoes including a member rotatably supported between adjacent ends of the shoes and mounted for shifting movement circumferentially of the drum with said shoes, said member having circumferentially spaced cam surfaces respectively engageable with the adjacent ends of the shoes for moving the latter outwardly relative to the drum upon rotation of the member in one direction, the rise of the cam surface engaging the shoe having the greatest wear being greater than the rise of the other cam surface by an amount predetermined to compensate for the different rates of Wear of the shoes and thereby secure uniform clearance between the shoes and braking surface of the drum, and means for rotating said member.

3. In brake mechanism, a revoluble brake drum, a backing plate for the drum fixed against rotation, brake friction means supported on the backing plate within the drum for shifting movement circumferentially of the drum and having spaced ends, a rotatable member extending into the drum between the ends of the friction means through an opening in the backing plate elongated to permit shifting movement of the member with the friction means, a cam secured to the member between the ends of the friction means and having diametrically opposed cam surfaces respectively engaging the ends of the friction means to move the latter outwardly relative to the drum upon rotation of the member in one direction, and means normally urging the member against the side wall of the opening opposite the wall facing the forward direction of rotation of the brake drum.

4. In brake mechanism, a revoluble brake drum, a backing plate for the drum fixed against rotation, brake friction means supported on the backing plate within the drum for shifting movement circumferentially of the drum and having spaced ends, a rotatable member extending into the drum between the ends of the friction means through an opening in the ba-cking plate elongated to permit shifting movement of the member with the friction means, a cam secured to the member within the drum and having circumferentially spaced cam surfaces eifective upon rotation of the member to respectively move the friction means outwardly relative to the drum, a flexible element secured to the member for movement as a unit with the latter, a plate shiftable with said member and held against rotation with the latter, and cooperating means on the plate and exible element for indicating predetermined increments of adjustment of the cam.

5. In brake mechanism, a revoluble brake drum, a backing plate for the drum xed against rotation, brake friction means supported on the backing plate within the drum for shifting movement circumferentially of the drum and having spaced ends, a rotatable member extending into the drum between the ends of the friction means through an opening in the backing plate elongated to permit shifting movement of the member with the friction means, a cam secured to the member between the ends of the friction means and having diametrically opposed cam surfaces respectively engaging the ends of the friction means to move the latter outwardly relative to the drum upon rotation of the member in one direction, a flexible disc secured to the member for movement as a unit therewith and having circumferentially spaced detents adjacent the periphery thereof, and a plate shiftable with said member and held against rotation by the latter, said plate having circumferentially spaced recesses successively engageable with the detents on the flexible disc to indicate predetermined ,increments of adjustment` of the cam.

6. In brake mechanism, a revoluble brake drum, a backing plate for the drum xed against rotation, brake friction means supported on the backing plate within the drum and having spaced ends, a rotatable member extending through the backing plate into the drum between said ends of the friction means, a cam secured to the member and having circumferentially spaced cam surfaces effective upon rotation of the member in one direction to respectively move the ends of the friction means outwardly relative to the brake drum, a flexible element rotatable as a unit with the member, a plate supported by the backing plate against rotation, and cooperating means on the plate and flexible element for indicating predetermined increments of adjustment of the cam.

7. In brake mechanism, a revoluble brake drum, a backing plate for the drum fixed against rotation, brake friction means supported on the backing plate within the drum and having spaced ends, a rotatable member extending-through the backing plate into the drum between said ends of the friction means, a cam secured to the member and having circumferentially spaced cam surfaces effective upon rotation of the member in one direction to respectively move the ends of the friction means outwardly relative to the brake drum, a discv secured to the member for movement as a unit therewith and having circumferentially spaced detents adjacent the periphery thereof, and a plate supported adjacent the disc and held against rotation, said plate having circumferentially spaced grooves successively engageable with the detents of the iiexible disc to indicate predetermined increments of adjustment of the cam.

8. In brake mechanism, a revoluble brake drum, a backing plate for the drum fixed against rotation, brake friction means supported on the backing plate within the drum for shifting movement circumferentially of the drum and having spaced ends, a cam rotatably supported between-said ends for shifting movement with the friction means ciroumferentially of the drum and having diametrically opposed cam surfaces respectively engaging the ends of the friction means to move the latter outwardly relative to the drum upon rotation of the cam in one direction, an abutment limiting shifting movement of the cam in one direction with the friction means, and means normally urging said cam to a position wherein shifting movement of the cam in the last named direction is prevented by said abutment.

9. In brake mechanism, a revoluble brake drum, a backing plate for the drum xed against rotation, brake friction means supported on the backing plate within the drum for shifting movement circumferentially of the drum and having spaced ends, a rotatable member extending into the drum between the ends of the friction means through an opening in the backing plate elongated to provide for shifting movement of the member with the friction means, a cam on the member between the ends of the friction means and having cam surfaces respectively engaging the ends of the friction means to move the latter outwardly relative to the drum upon rotation of the member in one direction, means accessible from a point exteriorly of the drum for rotating the member, and means normally urging the member in a direction circumferentially of the drum against one side wall of the opening aforesaid through the backing plate.

CARL F. BAISCH. 

